1. Field of the Invention
This invention relates generally to switch enclosures. More particularly, a low-cost, easy-to-manufacture and easy-to-use switch enclosure is described.
2. Description of the Related Art
Electrical switches are well-known in the art. Most electrical switches are comprised of two or more electrical contacts mounted within an insulating body. In many switches, the contacts extend through the insulating body, thus allowing electrical wires to be easily connected. Within the insulating body, the contacts are arranged so that at least one of the contacts can be moved into and out of contact with the other contact(s) by a suitable mechanical operating mechanism. When the contacts are engaged, electrical current flows from one contact to the other. Disengaging the contacts prevents current flow. Hereinafter, the contacts and the surrounding insulating body will be referred to as an electrical switch.
In many applications, an electrical switch is placed within a switch enclosure, often referred to as a housing. The housing protects the switch, including any wiring connected to the contacts, from environmental conditions and human contact. Typically, the housing is comprised of two parts which, when joined, form an interior cavity which surrounds the electrical switch. The housing also has two orifices. External electrical wires are passed through the first orifice and connected to the electrical switch, while an actuator, for mechanically communicating with the electrical switch, occupies the second orifice.
Previously, the housing has been constructed from metallic materials, such as zinc, which are electrically conductive. Because of the conductivity, prior switches have required an electrical insulator between the switch, with its exposed electrical connections, and the housing. Moreover, an additional wire was needed to ground the housing. This not only increased manufacturing costs, but also complicated device installation.
Often, the internal configuration of the cavity made wiring the switch difficult. Specifically, because the interior cavity did not have sufficient space to house excess wire, technicians had to precisely cut each wire. Unfortunately, the required precision typically increased installation time. Moreover, frequently each wire within the cavity had to be cut to a different length, further complicating the installation procedure.
Terminal screws were often used to connect the wiring to the switch. Unfortunately, terminal screws have two disadvantages. First, they are ill-suited for use with stranded wire, as the torsional force tends to separate the strands. Second, all the wires needed to be disconnected from the terminal screws to replace a malfunctioning switch. Once the switch was replaced, the wires would be reinserted into the terminal screws.
To secure the two halves of the metal housing together, screws were run through mounting holes in both halves. In previous designs, the mounting holes ran through the housing cavity, thus requiring an additional seal to prevent environmental elements from entering the cavity. Frequently, lead washers sealed the mounting holes and secured the screws in place. It was not uncommon for such washers to be crushed, thereby jamming the screw in place.
Finally, previous devices required a jam nut to secure the bushing for the over-travel plunger. Once again, this required extra parts and increased assembly time, thus adding to the cost of the product.